Passivation is a natural process that occurs on the surface of stainless steel, which forms a thin, protective oxide layer. This oxide layer, primarily composed of chromium oxide Cr2O3 , is what protects the stainless steel from corrosion. The mechanism of passivation in stainless steel can be explained in the following steps:1. Exposure to oxygen: When stainless steel is exposed to air or an oxygen-containing environment, the chromium present in the steel reacts with oxygen to form a thin oxide layer on the surface.2. Formation of chromium oxide layer: The chromium oxide Cr2O3 layer forms spontaneously and uniformly on the surface of the stainless steel. This layer is only a few nanometers thick but is highly stable, adherent, and corrosion-resistant.3. Self-healing property: One of the unique properties of the chromium oxide layer is its ability to self-heal. If the stainless steel surface is scratched or damaged, exposing the underlying metal, the chromium in the exposed area will react with oxygen to form a new oxide layer, effectively "healing" the damaged area and restoring the protective barrier.4. Protection against corrosion: The chromium oxide layer acts as a barrier between the stainless steel and the surrounding environment, preventing the penetration of corrosive elements such as water, oxygen, and other chemicals. This barrier reduces the rate of corrosion and helps maintain the structural integrity and appearance of the stainless steel.In summary, the mechanism of passivation in stainless steel involves the formation of a thin, protective chromium oxide layer on the surface, which acts as a barrier against corrosion. This layer is self-healing, ensuring that the stainless steel remains protected even if the surface is damaged.